A digital audio/video program is a collection of various audio and video segments arranged in a linear sequence. The method used to join each segment together is called a transition. Several common video transition methods are known, such as vertical cuts, wipes, dissolves, fades-to-black and fades-from-black.
A “cut” is an abrupt change from one scene to another and is the simplest and most basic transition method. The term “cut” comes from the process of film editing where two segments of film were physically cut and then spliced together to produce an instant transition. In modern digital video, the term “vertical cut” is used to indicate the transition that occurs at the vertical boundary between images of the video signal.
Time alteration of a video program is the process of adding or removing individual frames of video to lengthen or shorten the duration of the program. The challenge of time alteration is finding locations within the program to add or remove frames without the viewer noticing. The abrupt change of a vertical cut provides the perfect opportunity to remove or duplicate one or more video frames without any noticeable artifact.
Techniques for time alteration of the corollary audio signal are known to those skilled in the art. For example, commonly-assigned U.S. Pat. No. 7,092,774, entitled Multi-Channel Audi Processing System with Real-time Program Duration Alteration, incorporated herein by reference, discloses techniques operable in real-time to alter the running time of a program signal, and in particular, to techniques particularly suited to operate on multi-channel audio program signals.
It would be desirable to have corresponding methods for analyzing the video signal in order to concurrently alter the run time of both the audio and video signals in a digital audio/video program. In order to effectively do so for video signals, an effective method to detect vertical cuts in the video signal is required.